THE CHARACTERIZATION OF ELECTRODEPOSITED ZN-SIO2 COMPOSITES BEFORE AND AFTER CORROSION TEST

The microstructure of electrodeposited Zn-SiO2 composites before and after corrosion tests has been studied by using scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. As-deposited Zn-SiO2 composites are composed of SiO2-rich and SiO2-poor phases. After a wet and dry cyclic corrosion test, including NaCl solution spray, zinc hydroxychloride is formed on the SiO2-rich phase which surrounds the uncorroded SiO2-poor phase. Zinc hydroxide, zinc oxide and zinc hydroxychloride are also formed on the surface of the Zn-SiO2 composites. The high corrosion resistance of the composites is attributed to the formation of protective corrosion products in the composite layer supported by SiO2.